The vehicle detecting apparatus is installed at the roadside to collect the traffic information for instantaneously determining the traffic situation and monitoring the vehicle transportation for the traffic management. With the combination of the well-designed automatic assessment model, the vehicle detecting apparatus is able to provide the desired traffic information.
Regarding the existing vehicle detecting apparatuses, the loop-typed detector is commonly applied in the present transportation management system(TMS). The variation of electrical induction may occur and may be detected while the target vehicle passes the metallic loops of the detector that is arranged under the ground, and thereby the traffic flow as well as the vehicle occupancy would be obtainable. The speed and length of the vehicle are determined with the duration of passing two adjacent loops, and therewith the vehicle classification is further determined. Such detecting apparatus, however, is disadvantageous since the lanes need to be closed while the detecting apparatus is maintained, which causes a great inconvenience for the transportation management.
With respect to further detecting schemes, the use of Doppler radar for vehicle detection results in relatively accurate information for the vehicle speed. In order to obtain the maximum echo power, however, the wave transmitted by such radar exhibits the characteristic of uni-direction, and accordingly each Doppler radar is merely adoptable for the single-lane vehicle detection. The echo power of the Doppler radar may vary with the distance between the detecting apparatus and the target vehicle if such radar is applied for the multi-lane vehicle detection, so that the detection accuracy would be affected thereby. For this reason, it needs to arrange a dedicated detecting apparatus for each respective traffic lane if the traffic information for multiple lanes is desired, and such arrangement also causes extremely high set-up and maintain costs.
Moreover, the detecting apparatus using the Doppler radar is only suitable for speed detection, which fails in obtaining some further traffic parameters, such as the vehicle classification, the occupancy and the density, that are desired for the transportation management.
On the other hand, the remote traffic microwave detector adopting the frequency-modulation continuous-wave (FMCW) scheme is regarded as a generally cost-effective solution. Such detecting apparatus transmits FMCW signals with a fixed sector-shaped beam at a low power level, and the microwave beam may form an invisible ellipse trace above the road surface. In this case, the signal reflecting from any object will be transmitted to the detecting apparatus for the target detection and distance determination. It is believed that such apparatus is of great potential in the vehicle detection application.
Regarding the existing microwave detecting apparatus, the intermediate-frequency and digital signal processor thereof needs to carry out the post-stage signal process relating to the respective echo power of the signal that is reflecting from the targets of different distances, so as to determine the relevant traffic parameters. In this case, the functions of such detecting apparatus are still limited, and is disadvantageous in the relatively high cost due to the different designs thereof for the post-stage signal process.
According to the statement above, a vehicle detecting apparatus on different lanes at low cost is in need.